The present invention relates generally to compositions of matter, apparatuses and methods useful in detecting and identifying microorganisms causing or present in machine felts and on paper defects.
As described for example in U.S. Pat. Nos. 7,306,702 and 5,928,875, paper is produced in a continuous manner from a fibrous suspension (pulp furnish) generally made of water and cellulose fibers. A typical paper manufacturing process consists of 3 stages: forming, pressing, and drying. In the forming stage, dilute pulp furnish is directed on a wire or between 2 wires. The majority of the water is drained from the pulp furnish, through the wire, creating a wet paper web. In the pressing stage the paper web comes in contact with one or generally more porous Machine Felts that are used to extract much of the remaining water from the web. Often the pickup felt is the first felt that the wet paper web contacts which is used to remove the paper web from the wire, via a suction pickup roll positioned behind the felt, and then to transport the paper web to the rest of the press section. The paper web then generally passes through one or more presses each consisting of rotating press rolls and/or stationary elements such as press shoes that are positioned in close proximity to each other forming, what is commonly referred to as, a press nip. In each nip the paper web comes in contact with either one or two Machine Felts where water is forced from the paper web and into the press felt via pressure and/or vacuum. In single-felted press nips the paper web is in contact with the press roll on one side and the felt on the other. In double-felted press nips, the paper web passes between the two felts. After the press section, the paper web is dried to remove the remaining water, usually by weaving through a series of steam heated dryer cans.
Machine felts often consist of wool or nylon base fabric generally made of from 1 to 4 individual layers of filaments arranged in a weave pattern. An extruded polymeric membrane or mesh can also be included as one or more of the base fabric layers. Batt fibers, of smaller diameter than the base fabric filaments, are needled into the base on both sides giving the felt a thick, blanket-like appearance. Machine Felts are designed to quickly take in water from the paper web in the nip and hold the water so that it does not re-absorb back into the sheet as the paper and felt exit the press nip. Machine Felts are normally a belt passing through an endless loop that circulates continuously between sheet contact stages and return stages. Water pulled into the felt from the paper web at the nip is generally removed from the felt by vacuum during the felt return stage at, what is frequently referred to as, the uhle box.
Papermaking systems utilize several raw materials that introduce microorganisms into the machine system. This includes virgin wood fiber, recycled fiber, freshwater, starch, dyes, and other chemical additives. Microorganisms proliferate in many or all of the warm, nutrient rich environments present within papermaking systems and diverse microbial communities result. Inadequate control of microbial growth allows for the formation of surface deposits that slough, leading to filter or nozzle plugging and defects (e.g. spots or holes) or breaks in the sheet. Microorganisms can also proliferate in the felts and machine fabrics, negatively impacting water removal and machine or operational efficiency.
Microbial growth in papermaking systems can be quite harmful and costly. The growth of microorganisms on equipment surfaces can lead to the formation of deposits that slough and contribute to sheet defects and holes. Contaminated shower water treatments or process water can lead to the growth of microbes on felts which commonly result in the formation of plugs on the felts. These plugs in turn cause a number of problems most notably the impairment of water removal from paper web. As a result microbial growth can result in an excessive and costly need for multiple boil-outs and cleanings of felts or other papermaking equipment. These problems can be compounded when an incorrect determination of which microorganisms occurs because this can result in a treatment which further degrades the quality of the paper, further impacts process equipment, and/or may not even control the underlying microbial infestation. Moreover incorrectly distinguishing between biologically caused problems and mechanical or chemical caused problems can further result in inadequate, wasteful, and possibly counter-productive efforts.
A number of prior art methods are known for identifying which microorganisms are present in a papermaking system. These methods however are particularly deficient when applied to paper sheets or felts. Some of the prior art methods such as U.S. Pat. Nos. 8,012,758, 7,981,679, and 7,949,432 detect various effects in the fluids of the papermaking system produced by living microbiological organisms. Other methods such as U.S. Pat. No. 5,281,537 rely on obtaining a sample of living microorganism contaminant and growing more of it so as to perform various analyses. In the context of paper sheets and felts however these methods are particularly inadequate as by the time samples of the felt or paper are taken they no longer contain sufficient (or any) live organisms to culture or any of the chemical products that they produce. Also items of the papermaking system (such as paper sheets and felts) that are downstream from the heating or drying sections will have had all the defect causing microorganisms killed off after they have already caused the defects. Alternative methods that do not rely on the presence of live organisms also tend to be deficient because they often produce false positives. For example ninhydrin (which is used to detect primary or secondary amines) and IR spectroscopy often produce false positives or negatives because they detect materials that may have non-biological origins (such as chemical additives or contamination).
Thus it is clear that there is clear utility in novel methods and compositions for the proper identification of microorganisms present on machine felts and paper sheets. The art described in this section is not intended to constitute an admission that any patent, publication or other information referred to herein is “Prior Art” with respect to this invention, unless specifically designated as such. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 CFR §1.56(a) exists.